Taking the typical black soil farmland in Hailun City, Heilongjiang Province as an experimental sample area, the characteristics of soil animal community structure and its role in straw degradation under different straw returning methods in black soil area were studied. The degradation bags of 6, 30, and 260 meshes were selected and five treatments were set up including 17kg corn straw+2kg paddy returning+100% microbial concentration accelerator (sample A), 8.5kg corn straw+1kg paddy returning+50.0% microbial concentration accelerator (sample B), original sample (sample C), 8.5kg corn straw+1kg paddy returning (sample D), and 17kg corn straw+2kg paddy returning (sample E), respectively. The degradation rate of corn straw and the number of microorganisms were determined in each September from 2009 to 2011. The results showed that the cumulative straw degradation rate of all samples was more than 55.0%. The order of straw degradation rate was A > B > C > D > E. The main animal groups that played a major role in straw degradation were Oribatidae, Mesostigmata, and Arthropodiaceae, which accounted for 86.7% of the total number of soil animals. In the same treatment sample, the number and diversity of soil fauna in different size degradation bags were significantly different (P<0.001), while the number, type and diversity of soil fauna in different aperture degradation bags were positively correlated with the degradation rate of straw, which further indicated that soil fauna could promote the degradation of straw.